The invention relates to a vane-type compressor for use in an air conditioner and a cooling device in an automobile. A vane-type compressor of this general type is compact and does not create excessive vibration and noise.
FIGS. 1 through 3 show a conventional vane-type compressor which was constructed with a view of enhancing compression efficiency. In this compressor, an arcuate groove 8 is formed in an inner surface of a side housing 6. The arcuate groove 8 is in fluid communication with a space 211 defined by vane grooves 21 formed in a rotor 2 and bottoms 31 of vanes 21 slidingly disposed therein. This fluid communication is accomplished during the suction stroke of the pump at which time fluid pressure is applied to the bottom 31 of the vane 3 through an intake port 4, a fluid passage 7 formed in the side housing 6, a check valve 11 and the arcuate groove 8 to thus prevent the space 211 from being at a negative pressure. As a result, the sliding performance of vanes is improved to thus enhance the compression efficiency and abnormal wear of the inner surface of a rotor housing is avoided.
However, such a construction has drawbacks as follows.
During the suction stroke, the vane bottoms 31 are subject to intake fluid pressure from the intake port 4 through the fluid passage 7, check valve 11, and the arcuate groove 8. In this case, when the vanes go into a compression stroke following an intake stroke by the rotation of the rotor 2, the intake fluid pressure supplied into the space 211 of the vane groove is extremely high until the exhaust stroke. Accordingly, the pressure applied to the vane bottoms 31 is large thereby causing the vanes to be abnormally worn or even to be broken. Particularly, in the vane-type compressor of the lubrication type, the above-described drawback becomes significant since oil is mixed with Freon.TM. gas (coolant) for lubrication and this mixture is subjected to intake compression and exhaust strokes. Such lubricating oil is compressed within a working chamber during the compression stroke. Since the oil is non-compressive liquid, vane 3 is not sufficiently radially inwardly displaceable within the vane groove due to the oil accumulation at the vane bottom during compression stroke. As a result, rotation of the rotor may be prevented, and the vanes may be broken.